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In the work presented here, mesoporous titania (MT) powders is synthesized by sol-gel method using amphiphilic triblock copolymer as a template at two different levels of relative humidity (RH); 20 and 80%. Various techniques such as small angle X-ray diffraction (SAXRD), wide angle X-ray diffraction (XRD), UV-visible spectroscopy, high resolution transmission electron microscopy (HRTEM), Fourier transformed infra red (FTIR) spectroscopy and N 2-adsorption/desorption analysis were utilized to study the prepared samples. Further, the photocatalytic activities of the prepared samples were evaluated from the photo-degradation analysis of methylene blue (MB). For the sample treated with 80%RH the formation of an ordered mesoporous structure with a high specific surface area (172 m 2g -1), mesoporosity (48%) and enhanced photocatalytic activity were obtained compared to those of the sample subjected to 20%RH. The observed increased MB degradation for the latter is mainly attributed to the formation of higher specific surface area and mesoporosity. The availability of highly ordered open pore channels could provide increased contacts between reactants in the solution and the active sites on the surfaces of MT particles. Refereed/Peer-reviewed

In the work presented here attempt is made to investigate phase evolution and magnetic properties of Co/α-Fe2O3:1:6 (molar ratio) powder mixtures subjected to high energy milling (30 h) followed by annealing in air and subsequent heat-treatment in a reducing atmosphere at 400 °C for 20 min. The latter process gave rise to the formation of a nanocomposoite compound composed of CoFe2O4, Fe3O4 and α-Fe phases, as evidenced by Mossbauer and XRD results. Rather high maximum magnetization Mmax (88 emu/g) and reasonable iHC (1.03 kOe) values were obtained for the nanocomposite sample prepared. This is possibly attributed to the existence of well exchange coupled soft and hard magnetic phases. Further, the structural-magnetic properties relationship of the various powders prepared is discussed in detail.

Nanocrystalline alumina–zirconia powders were prepared by a modified chemical route using sucrose, polyvinyl alcohol (PVA) and metal nitrates followed by a post calcination process. The process involved dehydration of Al3+–Zr4+ ions-sucrose–PVA solution to a highly viscous liquid which on decomposition process produced a black precursor material. The obtained precursor were then calcined at various temperatures: 1,050, 1,100, 1,150, 1,200 and 1,250 °C for different soaking times (1, 2, 4 h) in air. The formation of a nanocomposite composed of α-alumina (~20 nm) and tetragonal (t) zirconia (~19 nm) crystallites were confirmed for the sample calcined at 1,200 °C for 2 h, based on our XRD and TEM results. However, for the samples calcined below 1,150 °C the composite formed were composed of metastable alumina (γ, δ, θ) as well as t-zirconia phases. Interestingly, the zirconia phase retained its tetragonal structure for all the samples calcined above 1,050 °C. This is possibly related to the “size effect” and reduction of surface enthalpy of the zirconia crystallites surrounded by Al3+ cations.

In this work attempt is made to synthesize PbTiO3(PT) nanopowder by low temperature direct synthesis (LTDS) method already introduced by Wada et al. [8]. Various samples were prepared by precipitating a strong acidic Ti-bearing solution in an alkaline solution obtained by dissolution of Pb(NO3)2 in a KOH solution (pH = 14). The samples were synthesized with varying Pb/Ti atomic ratios (1.0, 2.7, 6.5 and 10) at 70 ∘C. XRD, TEM, FTIR and DTA/TG techniques were utilized to characterize the obtained powders. The formation of single phase PT was not confirmed for the non-heat treated as precipitated samples in contrast with the results obtained by Wada et al. [8] for BaTiO3. Further, for the as precipitated samples not subjected to washing process with a Pb/Ti ratio above 1, the formation of unknown crystalline phase/s was detected due to the reaction taken place between Ti-bearing solution and potassium plumbate formed by dissolution of Pb(NO3)2 in KOH solution. Applying washing process for these samples gave rise to the partial destruction of the observed structure/s and the formation of an amorphous phase as confirmed by XRD and TEM results. However, calcination of the as precipitated/washed samples at 500 ∘C and 700 ∘C for 1 hour gave rise to the formation of PT nanopowder as the main phase with average crystallite sizes in the range of about 11–14.5 nm respectively. Single phase PT nanopowder of an average crystallite size of 13 nm was formed for the sample with a Pb/Ti ratio = 1 when calcined at 500 ∘C for 1 hour. For the calcined samples with Pb/Ti ratios above 1 the formation of PbO as the second phase, however, was also detected and its level of formation was found to be related to the Pb/Ti ratio.

In this work attempt is made to study the effects of the level of the addition of two dopant systems, that is, Nb2O5/Co2O3 and Ba(Nb2/3Co1/3)O3 on the structure, microstructure, and dielectric properties of BaTiO3(BT) prepared by ceramic route. For the BT samples doped with 2 and 3 at % Nb2O5/Co2O3 a broad maxima for er–T variations was observed. Higher levels of addition, that is, 6, 8, and 10 at % Nb2O5/Co2O3, however, caused a drastic reduction in the magnitude of er and vanishing of maxima peaks observed. The reduction in the magnitudes of the er for these samples is related to the observed reduction of the tetragonality of doped BT samples as well as the existence of some non-ferroelectric extra phase, evidenced by our XRD analysis. The existence of this extra phase is also believed to be mainly responsible for the observed increase of the dielectric loss. For the BT samples doped with Ba(Nb2/3Co1/3)O3 perovskite solid solution, the er maxima peak could only be detected for the samples doped with 2 at %. In the case of the samples doped with 4, 6, 8, and 10 at % perovskite solid solution, however, a very uniform distribution of er–T was observed. The increase of the level of dopant for these series of samples was also seen to give rise in the reduction of the magnitude of er. However, this reduction was not as strong as the cases observed for the samples doped with 8 and 10 at % Nb2O5/Co2O3. XRD patterns obtained for these series of samples also revealed the reduction of tetragonality of the BT samples when doped with Ba(Nb2/3Co1/3)O3. Further, microstructural studies carried out by scanning electron microscopy (SEM) on both series of samples revealed a contrasting picture. While a uniform grain size distribution was observed for the whole series of the samples doped with Ba(Nb2/3Co1/3)O3, a non-uniform size distribution of grain sizes was observed in the case of samples doped with Nb2O5/Co2O3. This is thought to be due to the possible formation and non-uniform distribution of a liquid phase due to the formation of Ti-rich region in the shell region of Nb2O5/Co2O3-doped samples. The existence of such liquid phase, in case of Nb2O5/Co2O3-doped samples, would have the consequence of an increased rate of diffusion of Nb/Co into the BT cores leaving narrow compositional fluctuations for the shell regions.

In this work, an attempt is made to study the effects of sintering temperature on the microstructure and high-frequency (HF) magnetic properties of a nickel zinc ferrite compound of very low ZnO content of Ni0.467Zn0.07Co0.015Fe0.511O4 composition. Samples were prepared by a conventional ceramic route and sintered for 2 h at 1150, 1200, 1250, and 1300 °C. It was shown that the higher the sintering temperature the higher the saturation magnetization and the measured initial permeabilities, and the lower was the H c of the samples. This was related to the increased sintered densities and grain sizes. The magnitudes of the electrical resistivity of the samples sintered at 1300 °C compared to those of the samples sintered at 1150 °C and 1200 °C showed four orders decrease. This is thought to be due to the grain-size increase and possibly the formation of higher Fe2+/Fe3+ concentration. The lowest measured quality factor (Q-factor) obtained in the range of 60–210 MHz, corresponds to the samples sintered at 1300 °C. The highest Q-value in the frequency range of 125–210 MHz was obtained for the samples sintered at 1150 °C, which has also shown the highest electrical resistivity.

In this work, an attempt is made to study \( Pb_{1 - x} Y_x \left( {Zr_{0.53} Ti_{0.47} } \right)O_3 \) system with x=0.0125, 0.025, 0.050, 0.075 and 0.1. It was shown that there is limited solid solubility (0.625 mol %) of \( Y_2 O_3 \) or 1.25 mol % of \( Y^{3 + } \) in PZT(53/47). For higher levels of dopant, mainly two other extra second phases were detected. The first was a Zr-rich phase in which some \( Y_{^2 } O_3 \) and small amounts of \( TiO_2 \) was dissolved. The second one was a Pb solid solution \(\left( {PbO_{SS} }\right)\) composed of mainly PbO, \(Y_2 O_3 \) and \(ZrO_2 \) which was initially also seen in calcined samples. The formation of Zr-rich phase is thought possibly to originate due to the sublimation of Pb from \(PbO_{SS}\) source during the sintering process. For higher x values, a structural shift towards Ti-rich region of PZT's phase diagram is seen. All piezoelectric parameters of the doped samples such as \(d_{33}\), \(g_{33}\) are seen to decline sharply compared to that of undoped samples. Increasing the level of dopant gave rise to the increase of conductivity and dielectric loss of sintered samples. The formation of non-ferroelectric extra phases, and the Zr/Ti change of the main formed phase is believed to be responsible for this behavior.